Redundant inline-bypass switch

ABSTRACT

An inline-bypass switch system includes: a first inline-bypass switch appliance having a first bypass component, a first switch coupled to the first bypass component, and a first controller; and a second inline-bypass switch appliance having a second bypass component, a second switch coupled to the second bypass component, and a second controller; wherein the first controller in the first inline-bypass switch appliance is configured to provide a state signal that is associated with a state of the first inline-bypass switch appliance; and wherein the second controller in the second inline-bypass switch appliance is configured to control the second bypass component based at least in part on the state signal.

FIELD

This application relates generally to network devices, and morespecifically, to inline-bypass switch appliances.

BACKGROUND

A switch appliance connected between two communicating network nodes mayinclude a switch for forwarding packets to an inline tool. The switchappliance may also include a bypass component to bypass the switch incertain situation. For example, if the switch appliance lost power, thenthe switch may not be able to forward packets to the inline tool. Insuch situation, the bypass component may provide a physical bridge totransmit the packets from a transmitting node to a receiving node,without passing the packets to the switch for forwarding to the inlinetool. However, in such solution, the packets would not be able to beprocessed by the inline tool.

SUMMARY

An inline-bypass switch system includes: a first inline-bypass switchappliance having a first bypass component, a first switch coupled to thefirst bypass component, and a first controller; and a secondinline-bypass switch appliance having a second bypass component, asecond switch coupled to the second bypass component, and a secondcontroller; wherein the first controller in the first inline-bypassswitch appliance is configured to provide a state signal that isassociated with a state of the first inline-bypass switch appliance; andwherein the second controller in the second inline-bypass switchappliance is configured to control the second bypass component based atleast in part on the state signal.

Optionally, the first switch is configurable to perform packetforwarding to a first set of one or more inline tools, and the secondswitch is configurable to perform packet forwarding to a second set ofone or more inline tools.

Optionally, the first bypass component and the second bypass componentare operable to place the inline-bypass switch system in one of at leastthree states, the three states comprising: a primary forwarding state inwhich the first inline-bypass switch appliance is configured to performpacket forwarding to the first set of the one or more inline tools; asecondary forwarding state in which the second inline-bypass switchappliance is configured to perform packet forwarding to the second setof the one or more inline tools; and a physical bypass state in whichthe first inline-bypass switch appliance does not perform packetforwarding to the first set of the one or more inline tools, and thesecond inline-bypass switch appliance does not perform packet forwardingto the second set of the one or more inline tools.

Optionally, the first controller is configured to provide the statesignal having a first value when the first bypass component in the firstinline-bypass switch appliance is in a relays-open state; and whereinthe second controller is configured to place the second bypass componentin the second inline-bypass switch appliance in a relays-closed statewhen the state signal has the first value.

Optionally, the first controller is configured to provide the statesignal having a second value that is different from the first value whenthe first bypass component in the first inline-bypass switch applianceis in a relays-closed state; and wherein the second controller isconfigured to place the second bypass component in the secondinline-bypass switch appliance in a relays-open state when the statesignal has the second value and when a packet forwarding path throughthe second switch has been established.

Optionally, the first inline-bypass switch appliance comprises a firstcommunication interface for receiving a packet from a network node, asecond communication interface for outputting the packet to the secondinline-bypass switch appliance, and a third communication interface foroutputting the state signal for reception by the second inline-bypassswitch appliance.

Optionally, the second inline-bypass switch appliance comprises a firstcommunication interface for receiving a packet from the firstinline-bypass switch appliance, a second communication interface foroutputting the packet to a network node, and a third communicationinterface for receiving the state signal from the first inline-bypassswitch appliance.

Optionally, the first bypass component has multiple relays; wherein whenthe relays are closed, the first bypass component is in a relays-closedstate, and when the relays are opened, the first bypass component is ina relays-open state.

Optionally, the first controller is configured to place the first bypasscomponent in the relays-open state when a packet forwarding path throughthe first switch has been established.

Optionally, the state signal has a value that represents the firstbypass component being in the relays-open state.

Optionally, the first controller is configured to place the first bypasscomponent in the relays-closed state when a packet forwarding paththrough the first switch has not been established.

Optionally, the state signal has a value that represents the firstbypass component being in the relays-closed state.

A first inline-bypass switch appliance includes: a first bypasscomponent; a first switch coupled to the first bypass component, thefirst switch configured to communicate with one or more inline tools; afirst controller configured to provide a state signal that is associatedwith a state of the first bypass component; a first communicationinterface configured to receive a packet from a first network node; asecond communication interface configured to output the packet to asecond inline-bypass switch appliance; and a third communicationinterface configured to output the state signal for reception by thesecond inline-bypass switch appliance.

Optionally, the first bypass component is operable to be in arelays-closed state, and is operable to be in a relays-open state;wherein when the first bypass component is in the relays-closed state,the first bypass component is configured to pass the packet from thefirst communication interface to the second communication interfacewithout passing the packet to the first switch; and wherein when thefirst bypass component is in the relays-open state, the first bypasscomponent is configured to pass the packet from the first communicationinterface to the first switch.

Optionally, the first bypass component comprises one or more relays.

Optionally, the first controller is configured to close the one or morerelays in the first bypass component when a packet forwarding paththrough the first switch has not been established or when the firstinline-bypass switch appliance is powered down; and wherein the firstcontroller is configured to open the one or more relays in the firstbypass component when the packet forwarding path through the firstswitch has been established.

Optionally, the state signal has a first value when the state of thefirst bypass component is in the first state, and wherein the statesignal has a second value that is different from the first value whenthe state of the first bypass component is in the second state.

Optionally, the first bypass component has one or more relays that areclosed whenever there is a power loss for the first inline-bypass switchappliance.

An inline-bypass switch system includes the first inline-bypass switchappliance, and the second inline-bypass switch appliance.

Optionally, the second inline-bypass switch appliance comprises: asecond bypass component; a second switch coupled to the second bypasscomponent; a second controller; a first communication interfaceconfigured to receive the packet from the second communication interfaceof the first inline-bypass switch appliance; a second communicationinterface configured to output the packet to a second network node; anda third communication interface configured to receive the state signal;wherein the second controller is configured to selectively place thesecond bypass component in a first state or a second state.

Optionally, the first state of the second bypass component comprises arelays-closed state, and the second state of the second bypass componentcomprises a relays-open state; wherein when the second bypass componentis in the relays-closed state, the second bypass component is configuredto pass the packet from the first communication interface of the secondinline-bypass switch appliance to the second communication interface ofthe second inline-bypass switch appliance without passing the packet tothe second switch; and wherein when the second bypass component is inthe relays-open state, the second bypass component is configured to passthe packet from the first communication interface of the secondinline-bypass switch appliance to the second switch.

Optionally, the second bypass component comprises one or more relays.

Optionally, the second controller is configured to close the one or morerelays in the second bypass component when one or more relays in thefirst bypass component are open; wherein the second controller isconfigured to open the one or more relays in the second bypass componentwhen the one or more relays in the first bypass component are closed,and when a packet forwarding path through the second switch has beenestablished; and wherein the second controller is configured to closethe one or more relays in the second bypass component when the one ormore relays in the first bypass component are closed, and when thepacket forwarding path through the second switch has not beenestablished.

Optionally, the second controller of the second inline-bypass switchappliance is configured to control the second bypass component based atleast in part on the state signal received from the first inline-bypassswitch appliance.

An inline-bypass switch appliance includes: a bypass component; a switchconfigured to communicate with one or more inline tools; a controller; afirst communication interface configured to receive a packet fromanother inline-bypass switch appliance; a second communication interfaceconfigured to output the packet to a network node; and a thirdcommunication interface configured to receive a state signal from theother inline-bypass switch appliance, the state signal being associatedwith a state of another bypass component in the other inline-bypassswitch appliance; wherein the controller is configured to control thebypass component based at least in part on the state signal.

Optionally, the bypass component is operable to be in a relays-closedstate, and is operable to be in a relays-open state; wherein when thebypass component is in the relays-closed state, the bypass component isconfigured to pass the packet from the first communication interface tothe second communication interface without passing the packet to theswitch; and wherein when the bypass component is in the relays-openstate, the bypass component is configured to pass the packet from thefirst communication interface to the switch.

Optionally, the bypass component comprises one or more relays.

Optionally, the controller is configured to close the one or more relaysin the bypass component when one or more relays in the other bypasscomponent are open; wherein the controller is configured to open the oneor more relays in the bypass component when the one or more relays inthe other bypass component are closed, and when a packet forwarding paththrough the switch has been established; and wherein the controller isconfigured to close the one or more relays in the bypass component whenthe one or more relays in the other bypass component are closed, andwhen the packet forwarding path through the switch has not beenestablished.

Other and further aspects and features will be evident from reading thefollowing detailed description of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of embodiments, in whichsimilar elements are referred to by common reference numerals. Thesedrawings are not necessarily drawn to scale. In order to betterappreciate how the above-recited and other advantages and objects areobtained, a more particular description of the embodiments will berendered, which are illustrated in the accompanying drawings. Thesedrawings depict only typical embodiments and are not therefore to beconsidered limiting of its scope.

FIG. 1 illustrates an inline-bypass switch appliance;

FIG. 2 illustrates the inline-bypass switch appliance of FIG. 1 in aforwarding state;

FIG. 3 illustrates the inline-bypass switch appliance of FIG. 1 in abypass state;

FIG. 4 illustrates an inline-bypass switch system that includes twoinline-bypass switch appliances;

FIG. 5 illustrates the inline-bypass switch system of FIG. 4 in aprimary forwarding state;

FIG. 6 illustrates the inline-bypass switch system of FIG. 4 in asecondary forwarding state;

FIG. 7 illustrates the inline-bypass switch system of FIG. 4 in a bypassstate;

FIG. 8A illustrates a state diagram for the first inline-bypass switchappliance in the inline-bypass switch system of FIG. 4;

FIG. 8B illustrates a state diagram for the second inline-bypass switchappliance in the inline-bypass switch system of FIG. 4;

FIG. 8C illustrates a state diagram for the inline-bypass switch systemof FIG. 4;

FIGS. 9A-9B illustrate state diagrams for the bypass components in theinline-bypass switch system of FIG. 4;

FIG. 10 illustrates another inline-bypass switch system that includestwo inline-bypass switch appliances;

FIG. 11 illustrates the inline-bypass switch system of FIG. 10 when bothappliances are operational;

FIG. 12 illustrates the inline-bypass switch system of FIG. 10 when oneof the appliances is in a bypass state;

FIG. 13 illustrates the inline-bypass switch system of FIG. 10 whenanother one of the appliances is in a bypass state; and

FIG. 14 illustrates the inline-bypass switch system of FIG. 10 when bothappliances are in a bypass state.

DESCRIPTION OF THE EMBODIMENTS

Various embodiments are described hereinafter with reference to thefigures. It should be noted that the figures are not drawn to scale andthat elements of similar structures or functions are represented by likereference numerals throughout the figures. It should also be noted thatthe figures are only intended to facilitate the description of theembodiments. They are not intended as an exhaustive description of theinvention or as a limitation on the scope of the invention. In addition,an illustrated embodiment needs not have all the aspects or advantagesshown. An aspect or an advantage described in conjunction with aparticular embodiment is not necessarily limited to that embodiment andcan be practiced in any other embodiments even if not so illustrated, ornot so explicitly described.

FIG. 1 illustrates an inline-bypass switch appliance 10. Theinline-bypass switch appliance 10 has a first communication interface 20for communication with a first node 22, and a second communicationinterface 24 for communication with a second node 26. The inline-bypassswitch appliance 10 also has a third communication interface 30 and afourth communication interface 32 for communication with an inline tool50. As shown in the figure, the inline-bypass switch appliance 10 alsoincludes a bypass component 60, a switch 70, and a controller 80. Thesecomponents are accommodated in a housing 90 so that the inline-bypassswitch appliance 10 may be transported, sold, and deployed as a unit.

The bypass component 60 is configured to selectively transmit packetsreceived from the node 22 and/or node 26 to the switch 70, orselectively bypass the switch 70 so that packets received at the firstcommunication interface 20 will be passed directly through the bypasscomponent 60 to the second communication interface 24, or vice versa.

The switch 70 is configured to pass packets to the inline tool 50 viathe third communication interface 30. After the inline tool 50 processesthe packets, the inline tool 50 then returns the packets to theinline-bypass switch appliance through the fourth communicationinterface 32. In the illustrated example, a pair of communicationinterfaces (i.e., communication interfaces 30, 32) is provided for oneinline tool 50. In other examples, the inline-bypass switch appliance 10may include multiple pairs of communication interfaces for communicationwith multiple inline tools. The switch 70 is configured to forward thepackets to one or more inline tools based on one or more parameters,such as IP source address, IP destination address, etc.

The controller 80 is configured to control the operation of the bypasscomponent 60 and the switch 70.

During use, the network nodes 22, 26 exchange packet traffic betweenthemselves connected through data links to the inline-bypass switchappliance 10, with the inline tool 50 attached to the inline-bypassswitch appliance 10 through data links. When the inline-bypass switchappliance 10 is powered up, the controller 80 may control the bypasscomponent 60 so that the bypass component 60 is either in arelays-closed state, or a relays-opened state.

As shown in FIG. 2, in the relays-opened state, each of the twocommunication interfaces 20, 24 of the inline-bypass switch appliance 10connected to the network nodes 22, 26 are coupled with ports on theswitch 70, which is configured to forward the traffic arriving at theseports to the communication interfaces 30, 32 linked to the inline tool50. Thus, when the relays in the bypass component 60 are opened, theinline-bypass switch appliance 10 is accordingly in a forwarding state.

As shown in FIG. 3, in the relays-closed state, the two communicationinterfaces 20, 24 of the inline-bypass switch appliance 10 connected tothe network nodes 22, 26 are physically coupled. As a result, trafficexchanged between the network nodes 22, 26 is directly delivered fromone communication interface (e.g., 20/24) to the other communicationinterface (e.g., 20/24). Thus, when the relays in the bypass component60 are closed, the inline-bypass switch appliance 10 is accordingly in abypass state.

When the inline-bypass switch appliance 10 is powered down or losespower unexpectedly, the bypass component 60 automatically enters therelays-closed state.

FIG. 4 illustrates an inline-bypass switch system 100 that includes twoinline-bypass switch appliances, i.e., a first inline-bypass switchappliance 10 a and a second inline-bypass switch appliance 10 b.

The inline-bypass switch appliance 10 a has a first communicationinterface 20 a for communication with a first node 22, and a secondcommunication interface 24 a for communication with the secondinline-bypass switch appliance 10 b. The inline-bypass switch appliance10 a also has a third communication interface 30 a and a fourthcommunication interface 32 a for communication with an inline tool 50 a.As shown in the figure, the inline-bypass switch appliance 10 a alsoincludes a bypass component 60 a, a switch 70 a, and a controller 80 a.These components are accommodated in a housing 90 a so that theinline-bypass switch appliance 10 a may be transported, sold, anddeployed as a unit.

In some cases, the first, second, third, and fourth communicationinterfaces 20 a, 24 a, 30 a, 32 a may be implemented using respectiveports. For example, in some cases, the first communication interface 20a may comprise a first network port for communication with the node 22,the second communication interface 24 a may comprise an appliance portfor communication with the second inline-bypass switch appliance 10 b,the third communication interface 30 a may comprise a first instrumentport for communication with the inline tool 50 a, and the fourthcommunication interface 32 a may comprise a second instrument port forcommunication with the inline tool 50 a. Also, in some cases, two ormore of the ports may be combined, and be implemented as a single port.

The bypass component 60 a is configured to selectively transmit packetsreceived from the node 22 to the switch 70 a, or selectively bypass theswitch 70 a so that packets received at the first communicationinterface 20 a will be passed directly through the bypass component 60 ato the second communication interface 24 a. In some cases, the bypasscomponent 60 a may include physical relays that can be opened or closedin response to one or more control signals. In other cases, the bypasscomponent 60 a may include logical relays that are implemented usingsoftware.

The switch 70 a is configured to pass packets to the inline tool 50 avia the third communication interface 30 a. After the inline tool 50 aprocesses the packets, the inline tool 50 a then returns the packets tothe inline-bypass switch appliance 10 a through the fourth communicationinterface 32 a. In the illustrated example, a pair of communicationinterfaces (i.e., communication interfaces 30 a, 32 a) is provided forone inline tool 50 a. In other examples, the inline-bypass switchappliance 10 a may include multiple pairs of communication interfacesfor communication with multiple inline tools. The switch 70 a isconfigured to forward the packets to one or more inline tools based onone or more parameters, such as IP source address, IP destinationaddress, etc.

In one or more embodiments, the switch 70 a may be configured to providepacket transmission in accordance with a pre-determined transmissionscheme. In some embodiments, the switch 70 a may be user-configurablesuch that packets may be transmitted in a one-to-one configuration(i.e., from one network port to an instrument port). As used in thisspecification, the term “instrument port” refers to any port that isconfigured to transmit packets to an instrument, such as inline tool(e.g., an intrusion prevention system, etc.). Also, a “network port” maybe an example of the communication interface 20 a, or the communicationinterface 24 a. In other embodiments, the switch 70 a may be configuredsuch that the packets may be transmitted in a one-to-many configuration(i.e., from one network port to multiple instrument ports). In otherembodiments, the switch 70 may be configured such that the packets maybe transmitted in a many-to-many configuration (i.e., from multiplenetwork ports to multiple instrument ports). In further embodiments, theswitch 70 may be configured such that the packets may be transmitted ina many-to-one configuration (i.e., from multiple network ports to oneinstrument port). In some embodiments, the one-to-one, one-to-many,many-to-many, and many-to-one configurations are all available forallowing a user to selectively configure the inline-bypass switchappliance 10 a so that the packets (or certain types of packets) arerouted according to any one of these configurations. In someembodiments, the packet movement configuration is predetermined suchthat when the inline-bypass switch appliance 10 a receives the packets,the inline-bypass switch appliance 10 a will automatically forward thepackets to the ports based on the predetermined packet movementconfiguration (e.g., one-to-one, one-to-many, many-to-many, andmany-to-one).

The controller 80 a is configured to control the operation of the bypasscomponent 60 a and the switch 70 a.

Although one communication interface 24 a is shown connecting the firstinline-bypass switch appliance 10 a to the second inline-bypass switchappliance 10 b, in other embodiments, there may be multiplecommunication interfaces 24 a (e.g., ports) for communicating packetsbetween the first and second inline-bypass switch appliances 10 a, 10 b.In such cases, there may be multiple bypass components 60 a coupling tothe respective communication interfaces 24 a. Also, there may bemultiple communication interfaces 20 a coupling to the respective bypasscomponents 60 a for receiving packets from one or more network nodes 22.

The second inline-bypass switch appliance 10 b has a first communicationinterface 20 b for communication with the first inline-bypass switchappliance 10 a, and a second communication interface 24 b forcommunication with the second node 26. The second inline-bypass switchappliance 10 b also has a third communication interface 30 b and afourth communication interface 32 b for communication with an inlinetool 50 b. As shown in the figure, the inline-bypass switch appliance 10b also includes a bypass component 60 b, a switch 70 b, and a controller80 b. These components are accommodated in a housing 90 b so that theinline-bypass switch appliance 10 b may be transported, sold, anddeployed as a unit.

In some cases, the first, second, third, and fourth communicationinterfaces 20 b, 24 b, 30 b, 32 b may be implemented using respectiveports. For example, in some cases, the first communication interface 20b may comprise an appliance port for communication with the firstinline-bypass switch appliance 10 a, the second communication interface24 b may comprise a network port for communication with the node 26, thethird communication interface 30 b may comprise a first instrument portfor communication with the inline tool 50 b, and the fourthcommunication interface 32 b may comprise a second instrument port forcommunication with the inline tool 50 b. Also, in some cases, two ormore of the ports may be combined, and be implemented as a single port.

The bypass component 60 b is configured to selectively transmit packetsreceived from the first inline-bypass switch appliance 10 a to theswitch 70 b, or selectively bypass the switch 70 b so that packetsreceived at the first communication interface 20 b will be passeddirectly through the bypass component 60 b to the second communicationinterface 24 b. In some cases, the bypass component 60 b may includephysical relays that can be opened or closed in response to one or morecontrol signals. In other cases, the bypass component 60 b may includelogical relays that are implemented using software.

The switch 70 b is configured to pass packets to the inline tool 50 bvia the third communication interface 30 b. After the inline tool 50 bprocesses the packets, the inline tool 50 b then returns the packets tothe inline-bypass switch appliance 10 b through the fourth communicationinterface 32 b. In the illustrated example, a pair of communicationinterfaces (i.e., communication interfaces 30 b, 32 b) is provided forone inline tool 50 b. In other examples, the inline-bypass switchappliance 10 b may include multiple pairs of communication interfacesfor communication with multiple inline tools. The switch 70 b isconfigured to forward the packets to one or more inline tools based onone or more parameters, such as IP source address, IP destinationaddress, etc.

In one or more embodiments, the switch 70 b may be configured to providepacket transmission in accordance with a pre-determined transmissionscheme. In some embodiments, the switch 70 b may be user-configurablesuch that packets may be transmitted in a one-to-one configuration(i.e., from one network port to an instrument port). A “network port”may be an example of the communication interface 20 b, or thecommunication interface 24 b. In other embodiments, the switch 70 b maybe configured such that the packets may be transmitted in a one-to-manyconfiguration (i.e., from one network port to multiple instrumentports). In other embodiments, the switch 70 b may be configured suchthat the packets may be transmitted in a many-to-many configuration(i.e., from multiple network ports to multiple instrument ports). Infurther embodiments, the switch 70 b may be configured such that thepackets may be transmitted in a many-to-one configuration (i.e., frommultiple network ports to one instrument port). In some embodiments, theone-to-one, one-to-many, many-to-many, and many-to-one configurationsare all available for allowing a user to selectively configure theinline-bypass switch appliance 10 b so that the packets (or certaintypes of packets) are routed according to any one of theseconfigurations. In some embodiments, the packet movement configurationis predetermined such that when the inline-bypass switch appliance 10 breceives the packets, the inline-bypass switch appliance 10 b willautomatically forward the packets to the ports based on thepredetermined packet movement configuration (e.g., one-to-one,one-to-many, many-to-many, and many-to-one).

The controller 80 b is configured to control the operation of the bypasscomponent 60 b and the switch 70 b.

Although one communication interface 20 b is shown connecting the secondinline-bypass switch appliance 10 b to the first inline-bypass switchappliance 10 a, in other embodiments, there may be multiplecommunication interfaces 20 b (e.g., ports) for communicating packetsbetween the first and second inline-bypass switch appliances 10 a, 10 b.In such cases, there may be multiple bypass components 60 b coupling tothe respective communication interfaces 20 b. Also, there may bemultiple communication interfaces 24 b coupling to the respective bypasscomponents 60 b for outputting packets to one or more network nodes 26.

As shown in FIG. 4, each of the inline-bypass switch appliances 10 a, 10b has the same configuration as that shown in FIG. 1, except that theappliance 10 a has a communication interface 102 a, and that theappliance 10 b has a communication interface 102 b, for communicationwith each other through a signaling link 110. The controller 80 a and/orthe controller 80 b is configured to control the first inline-bypassswitch appliance 10 a and the second inline-bypass switch appliance 10b, so that the inline-bypass switch system 100 can be selectively placedin (1) a primary forwarding state, (2) a secondary forwarding state, or(3) a bypass state.

In the primary forwarding state, the first inline-bypass switchappliance 10 a is configured to receive packet form the node 22, andpass the packet to the inline tool 50 a through the switch 70 a, whilethe second inline-bypass switch appliance 10 b is configured to pass thepacket for reception by the node 26 without going through the switch 70b and the inline tool 50 b. The primary forwarding state may be achievedby opening the relays in the bypass component 60 a in the firstinline-bypass switch appliance 10 a, and closing the relays in thebypass component 60 b in the second inline-bypass switch appliance 10 b.

In the secondary forwarding state, the first inline-bypass switchappliance 10 a is configured to receive packet form the node 22, andpass the packet to the second inline-bypass switch appliance 10 bwithout going through the switch 70 a and the inline tool 50 a. Such maybe accomplished by closing the relays in the bypass component 60 a inthe first inline-bypass switch appliance 10 a. The second inline-bypassswitch appliance 10 b receives the packet from the first inline-bypassswitch appliance 10 a, and passes the packet to the inline tool 50 bthrough the switch 70 b. Such may be accomplished by opening the relaysin the bypass component 60 b in the second inline-bypass switchappliance 10 b. After the inline tool 50 b processes the packet, thepacket is transmitted back to the second inline-bypass switch appliance10 b, which then passes the packet for reception by the node 26.

In the bypass state, both the relays in the bypass component 60 a in thefirst inline-bypass switch appliance 10 a, and the relays in the bypasscomponent 60 b in the second inline-bypass switch appliance 10 b, areclosed. Accordingly, in the bypass state, the first inline-bypass switchappliance 10 a receives packet from the node 22, and passes the packetto the second inline-bypass switch appliance 10 b without going throughthe switch 70 a and the inline tool 50 a. The second inline-bypassswitch appliance 10 b receives the packet from the first inline-bypassswitch appliance 10 a, and passes the packet to the node 26 withoutgoing through the switch 70 b and the inline tool 50 b.

In one implementation, the controller 80 a of the first inline-bypassswitch appliance 10 a (which functions as the primary switch appliancein the example) is configured to drive the signaling link “down” (e.g.,provide a state signal “down” via the signaling link 110) whenever thefirst inline-bypass switch appliance 10 a is down (which may be due toloss of power, etc.) so that it is unable to forward packets to theinline tool 50 a. In this situation, the first bypass component 60 a isin the relays-closed state, wherein the relays in the first bypasscomponent 60 a are closed. Also, the controller 80 a of the firstinline-bypass switch appliance 10 a is configured to drive the signalinglink “up” (e.g., provide a state signal “up” via the signaling link 110)whenever the first inline-bypass switch appliance 10 a is up so that itis able to forward packets to the inline tool 50 a. In this situation,the first bypass component 60 a is in the relays-open state, wherein therelays in the first bypass component 60 a are opened to pass packets tothe switch 70 a for forwarding packets to the inline tool 50 a. Thecontroller 80 b of the second inline-bypass switch appliance 10 b (whichfunctions as the secondary switch appliance in this example) isconfigured to sense the state of the signaling link 110, and control thesecond bypass component 60 b in the second inline-bypass switchappliance 10 b based at least in part on the state signal provided bythe signaling link 110. In particular, the controller 80 b may beconfigured to control the bypass component 60 b to place it in therelays-closed state whenever the signaling link 110 is sensed to be“up”, or whenever packet forwarding path through the switch 70 b forforwarding packets to the inline tool 50 b has not been established(e.g., during boot-up of the appliance 10 b, etc.). Also, the controller80 b may be configured to control the bypass component 60 b to place itin the relays-open state whenever the signaling link 110 is sensed to bedown, and when the packet forwarding path through the switch 70 b forforwarding packets to the inline tool 50 b has been established. Also,in one implementation, when the first inline-bypass switch appliance isunpowered, its bypass component 60 a is naturally in the relays-closedstate. Similarly, when the second inline-bypass switch appliance isunpowered, its bypass component 60 b is naturally in the relays-closedstate.

The primary forwarding state, the a secondary forwarding state, and thebypass state of the inline-bypass switch system 100 will be described infurther detail below with reference to FIGS. 5-7.

As shown in FIG. 5, the inline-bypass switch system 100 may beselectively placed in a primary forwarding state in which the firstinline-bypass switch appliance is configured to forward packets to theinline tool 50 a. Such may be performed in response to certaincondition, e.g., when the first inline-bypass switch appliance 10 a isup, and is able to forward packets to the inline tool 50 a through itsswitch 70 a.

In the primary forwarding state, a packet from the node 22 (which is anetwork transmitting node in the example) is received at the firstcommunication interface 20 a of the first inline-bypass switch appliance10 a. The relays in the bypass component 60 a are opened to allow thepacket to be passed to the switch 70 a. The switch 70 a then forwardsthe packet to the inline tool 50 a through the third communicationinterface 30 a at the first inline-bypass switch system 10 a. After theinline tool 50 a processes the packet, the inline tool 50 a thentransmits the packet to the fourth communication interface 32 a at firstinline-bypass switch apparatus 10 a. The packet is processed by theswitch 70 a, which passes the packet to the second communicationinterface 24 a. The packet exits from the communication interface 24 a,and is transmitted to the first communication interface 20 b at thesecond inline-bypass switch appliance 10 b. In the second inline-bypassswitch appliance 10 b, the relays in the bypass component 60 b areclosed for allowing the packet to be transmitted to the secondcommunication interface 24 b for reception by the node 26 (which is anetwork receiving node in the example) without going through the switch70 b at the second inline-bypass switch appliance 10 b.

In the illustrated embodiments, the controller 80 a at the firstinline-bypass switch apparatus 10 a and the controller 80 b at thesecond inline-bypass switch apparatus 10 b are configured to communicatewith each other so that the first controller 80 a at the firstinline-bypass switch apparatus 10 a can control the bypass component 60a and the switch 70 a in the first inline-bypass switch apparatus 10 a,and the second controller 80 b at the second inline-bypass switchapparatus 10 b can control the bypass component 60 b and the switch 70 bin the second inline-bypass switch apparatus 10 b, to achieve theprimary forwarding state as that shown in FIG. 5. For example, to placethe system 100 in the primary forwarding state, the controller 80 adrives a state signal of “up” through the signaling link 110, informingthe second inline-bypass switch appliance 10 b that the firstinline-bypass switch appliance 10 a is in the packet forwarding state.The controller 80 b at the second inline-bypass switch apparatus 10 bcontrols the bypass component 60 b based at least in part on the statesignal. Since the state signal is “up” (representing that the firstinline-bypass switch appliance 10 a is forwarding packets to inline tool50 a via its switch 70 a), the relays in the bypass component 60 b inthe second inline-bypass switch appliance 10 b are closed.

As shown in FIG. 6, the inline-bypass switch system 100 may also beselectively placed in a secondary forwarding state, in which the secondinline-bypass switch apparatus 10 b is configured to forward packets toits associated inline tool 50 b. Such may be performed in response tocertain condition, e.g., when the first inline-bypass switch appliance10 a is down, when the first inline-bypass switch appliance 10 a isbeing powered down, when the first inline-bypass switch appliance 10 ais not capable of forwarding packets to its associated inline tool 50 a,etc.

In the secondary forwarding state, a packet from the node 22 (which is anetwork transmitting node in the example) is received at the firstcommunication interface 20 a of the first inline-bypass switch appliance10 a. The relays in the bypass component 60 a are closed to allow thepacket to be passed to the second communication interface 24 a withoutgoing through the switch 70 a at the first inline-bypass switchappliance 10 a. The packet exits from the communication interface 24 a,and is transmitted to the first communication interface 20 b at thesecond inline-bypass switch appliance 10 b. In the second inline-bypassswitch appliance 10 b, the relays in the bypass component 60 b areopened for passing the packet to the switch 70 b in the secondinline-bypass switch apparatus 10 b. The switch 70 b then forwards thepacket to the inline tool 50 b through the third communication interface30 b. After the inline tool 50 b processes the packet, the inline tool50 b then transmits the packet to the fourth communication interface 32b at inline-bypass switch apparatus 10 b. The packet is processed by theswitch 70 b, which passes the packet to the second communicationinterface 24 b for forwarding to the node 26 (which is the networkreceiving node in the example).

In the illustrated embodiments, the controller 80 a at the firstinline-bypass switch apparatus 10 a and the controller 80 b at thesecond inline-bypass switch apparatus 10 b are configured to communicatewith each other so that the first controller 80 a at the firstinline-bypass switch apparatus 10 a can control the bypass component 60a and the switch 70 a in the first inline-bypass switch apparatus 10 a,and the second controller 80 b at the second inline-bypass switchapparatus 10 b can control the bypass component 60 b and the switch 70 bin the second inline-bypass switch apparatus 10 b, to achieve thesecondary forwarding state as that shown in FIG. 6. For example, toplace the system 100 in the secondary forwarding state, the controller80 a drives a state signal of “down” through the signaling link 110,informing the second inline-bypass switch appliance 10 b that the firstinline-bypass switch appliance 10 a is not in the packet forwardingstate. The controller 80 b at the second inline-bypass switch apparatus10 b controls the bypass component 60 b based at least in part on thestate signal. Since the state signal is “down” (representing that thefirst inline-bypass switch appliance 10 a not is forwarding packets toinline tool 50 a via its switch 70 a), the relays in the bypasscomponent 60 b in the second inline-bypass switch appliance 10 b areopened, thereby allowing the switch 70 b at the second inline-bypassswitch appliance 10 b to forward packets to the inline tool 50 b.

As shown in FIG. 7, the inline-bypass switch system 100 may also beselectively placed in a bypass state, in which packets from the networktransmitting node 22 is not forwarded to the inline tools 50 a, 50 b,but are instead passed to the network receiving node 26 without beingprocessed by the inline tools 50 a, 50 b. Such may be performed inresponse to certain condition, e.g., when the first inline-bypass switchappliance 10 a and the second inline-bypass switch appliance 10 b aredown, when the first inline bypass switch appliance 10 a and the secondinline-bypass switch appliance 10 b are being powered down, when both ofthe switch appliances 10 a, 10 b are not capable of forwarding packetsto their respective inline tools 50 a, 50 b, etc.

In the bypass state, a packet from the node 22 is received at the firstcommunication interface 20 a of the first inline-bypass switch appliance10 a. The relays in the bypass component 60 a are closed to allow thepacket to be passed to the second communication interface 24 a withoutgoing through the switch 70 a at the first inline-bypass switchappliance 10 a. The packet exits from the communication interface 24 a,and is transmitted to the first communication interface 20 b at thesecond inline-bypass switch appliance 10 b. In the second inline-bypassswitch appliance 10 b, the relays in the bypass component 60 b areclosed to allow the packet to be passed to the second communicationinterface 24 b for reception by the network receiving node 26 withoutgoing through the switch 70 b at the second inline-bypass switchappliance 10 b.

In the illustrated embodiments, since the bypass components 60 a, 60 bare naturally in the relays-closed state, when both the first and secondinline-bypass switch appliances 10 a, 10 b are down, the relays in thebypass components 60 a, 60 b are automatically closed. In the otherembodiments, the controller 80 a at the first inline-bypass switchapparatus 10 a and the controller 80 b at the second inline-bypassswitch apparatus 10 b are configured to communicate with each other sothat the first controller 80 a at the first inline-bypass switchapparatus 10 a can control the bypass component 60 a and the switch 70 ain the first inline-bypass switch apparatus 10 a, and the secondcontroller 80 b at the second inline-bypass switch apparatus 10 b cancontrol the bypass component 60 b and the switch 70 b in the secondinline-bypass switch apparatus 10 b, to achieve the bypass state as thatshown in FIG. 7.

It should be noted that the direction of packet flow may be oppositefrom the examples described. For example, in other cases, the node 26may be a network transmitting node, and the node 22 may be a networkreceiving node.

When the node 26 is a network transmitting node, in the primaryforwarding state, a packet from the node 26 is received at the secondcommunication interface 24 b of the second inline-bypass switchappliance 10 b. The relays in the bypass component 60 b are opened toallow the packet to be passed to the switch 70 b. The switch 70 b thenforwards the packet to the inline tool 50 b through the fourthcommunication interface 32 b at the second inline-bypass switch system10 b. After the inline tool 50 b processes the packet, the inline tool50 b then transmits the packet to the third communication interface 30 bat the second inline-bypass switch apparatus 10 b. The packet isprocessed by the switch 70 b, which passes the packet to the firstcommunication interface 20 b. The packet exits from the firstcommunication interface 20 a, and is transmitted to the secondcommunication interface 24 a at the first inline-bypass switch apparatus10 a. In the first inline-bypass switch appliance 10 a, the relays inthe bypass component 60 a are closed for allowing the packet to betransmitted to the first communication interface 20 a for reception bythe node 22 (which is a network receiving node in the example) withoutgoing through the switch 70 a at the first inline-bypass switchappliance 10 a.

When the node 26 is a network transmitting node, in the secondaryforwarding state, a packet from the node 26 is received at the secondcommunication interface 24 b of the second inline-bypass switchappliance 10 b. The relays in the bypass component 60 b are closed toallow the packet to be passed to the first communication interface 20 bwithout going through the switch 70 b at the second inline-bypass switchappliance 10 b. The packet exits from the first communication interface20 b, and is transmitted to the second communication interface 24 a atthe first inline-bypass switch apparatus 10 a. In the firstinline-bypass switch appliance 10 a, the relays in the bypass component60 a are opened for passing the packet to the switch 70 a in the firstinline-bypass switch apparatus 10 a. The switch 70 a then forwards thepacket to the inline tool 50 a through the fourth communicationinterface 32 a. After the inline tool 50 a processes the packet, theinline tool 50 a then transmits the packet to the third communicationinterface 30 a at the first inline-bypass switch apparatus 10 a. Thepacket is processed by the switch 70 a, which passes the packet to thefirst communication interface 20 a for forwarding to the node 22 (whichis the network receiving node in the example).

When the node 26 is a network transmitting node, in the bypass state, apacket from the node 26 is received at the second communicationinterface 24 b of the second inline-bypass switch appliance 10 b. Therelays in the bypass component 60 b are closed to allow the packet to bepassed to the first communication interface 20 b without going throughthe switch 70 b at the second inline-bypass switch appliance 10 b. Thepacket exits from the first communication interface 20 b, and istransmitted to the second communication interface 24 a at the firstinline-bypass switch apparatus 10 a. In the first inline-bypass switchappliance 10 a, the relays in the bypass component 60 a are closed toallow the packet to be passed to the first communication interface 20 afor reception by the network receiving node 22 without going through theswitch 70 a at the first inline-bypass switch appliance 10 a.

As discussed, the inline-bypass switch system 100 can be selectivelyplaced in (1) the primary forwarding state, (2) the secondary forwardingstate, or (3) the bypass state. FIGS. 8A-8C illustrate, respectively, astate diagram for the primary system (which may be one of the firstinline-bypass switch appliance 10 a and the second inline-bypass switchappliance 10 b), a state diagram for the secondary system (which may bethe other one of the first inline-bypass switch appliance 10 a and thesecond inline-bypass switch appliance 10 b), and a state diagram for theinline-bypass switch system 100 that includes the first inline-bypassswitch appliance 10 a and the second inline-bypass switch appliance 10b. For the purpose of the discussion below, it will be assumed that thefirst inline-bypass switch appliance 10 a is the primary system, andthat the second inline-bypass switch appliance 10 b is the secondarysystem. However, the scenario may be reversed.

As shown in the state diagram in FIG. 8A for the primary system (i.e.,the first inline-bypass switch appliance 10 a in the example), the firstinline-bypass switch appliance 10 a may be in a powered down state, in apath establishing state, or in a forwarding state. When the firstinline-bypass switch appliance 10 a is in the powered down state, theinline-bypass switch appliance 10 a has no power (e.g., due to powerloss, or power is turned off), the relays in the bypass component 60 aare closed, the signaling link 110 transmits a state signal of “down”(indicating that the relays in the bypass component 60 a in the firstinline-bypass switch appliance 10 a are closed) from the firstinline-bypass switch appliance 10 a to the second inline-bypass switchappliance 10 b, and there is no packet forwarding path established forforwarding packet to the inline tool 50 a (i.e., no packet forwardingpath through the switch 70 a).

When power is turned on at the first inline-bypass switch appliance 10a, the inline-bypass switch appliance 10 a is then placed in the pathestablishing state. In the path establishing state, the power in thefirst inline-bypass switch appliance 10 a is on, the relays in thebypass component 60 a are closed, the state signal transmitted by thesignaling link 110 is still “down”, and there is no packet forwardingpath for forwarding packet to the inline tool 50 a (i.e., no packetforwarding path through the switch 70 a). There is no packet forwardingpath because the path is in the progress of being established, and hasnot yet been established.

After a forwarding path for forwarding packet to the inline tool 50 ahas been established, the first inline-bypass switch appliance 10 a isthen in the forwarding state. In the forwarding state, the power in thefirst inline-bypass switch appliance 10 a remains on, the relays in thebypass component 60 a are opened, the signaling link 110 transmits astate signal of “up” (indicating that the relays in the bypass component60 a in the first inline-bypass switch appliance 10 a are opened) fromthe first inline-bypass switch appliance 10 a to the secondinline-bypass switch appliance 10 b, and the forwarding path has beenestablished.

If there is a power loss, or a powered down command, then the firstinline-bypass switch appliance 10 a may be placed back in the powereddown state. The powered down command may be generated by the controller80 a, or a user command that is received by the first inline-bypassswitch appliance 10 a.

As shown in the state diagram in FIG. 8B for the secondary system (i.e.,the second inline-bypass switch appliance 10 b in the example), thesecond inline-bypass switch appliance 10 b may be in a powered downstate, in a path establishing state, in a forwarding state, or in abypass state. When the second inline-bypass switch appliance 10 b is inthe powered down state, the inline-bypass switch appliance 10 b has nopower (e.g., due to power loss, or power is turned off), the relays inthe bypass component 60 b are closed, signal from the signaling link 110is ignored, and there is no packet forwarding path established forforwarding packet to the inline tool 50 b (i.e., no packet forwardingpath through the switch 70 b).

When power is turned on at the second inline-bypass switch appliance 10b, the inline-bypass switch appliance 10 b is then placed in the pathestablishing state. In the path establishing state, the power in thesecond inline-bypass switch appliance 10 b is on, the relays in thebypass component 60 b remains closed, signal from the signaling link 110is ignored, and there is still no packet forwarding path established forforwarding packet to the inline tool 50 b.

After a forwarding path for forwarding packet to the inline tool 50 bhas been established, the second inline-bypass switch appliance 10 b maythen be placed in either the forwarding state or the bypass state. Ifthe signaling link 110 has sent a state signal of “down” from the firstinline-bypass switch appliance 10 a to the second inline-bypass switchappliance 10 b, the second inline-bypass switch appliance 10 b is thenplaced in the forwarding state. On the other hand, if the signaling link110 has sent a state signal of “up” from the first inline-bypass switchappliance 10 a to the second inline-bypass switch appliance 10 b, thenthen second inline-bypass switch appliance 10 b is placed in the bypassstate. In the forwarding state, the power in the second inline-bypassswitch appliance 10 b remains on, the relays in the bypass component 60b are opened, the signaling link 110 has transmitted a state signal of“down” (indicating that the relays in the bypass component 60 a in thefirst inline-bypass switch appliance 10 a are closed), and theforwarding path (for forwarding packets to the inline tool 50 b) hasbeen established. When the second inline-bypass switch appliance 10 b isin the forwarding state, packets may be forwarded to the inline tool 50b through the switch 70 b in the second inline-bypass switch appliance10 b

In some cases, if the signaling link 110 has transmitted a state signalof “up” from the first inline-bypass switch appliance 10 a to the secondinline-bypass switch appliance 10 b, then the second inline-bypassswitch appliance 10 b is transitioned into the bypass state. In thebypass state, the relays in the bypass component 60 b are closed,thereby allowing packets to be passed through the second inline-bypassswitch appliance 10 b without having the packets go through the switch70 b and the inline tool 50 b. If the signaling link 110 later sends astate signal of “down” (indicating that the relays in the bypasscomponent 60 a in the first inline-bypass switch appliance 10 a areclosed), then the second inline-bypass switch appliance 10 b is placedin the forwarding state, wherein packets are forwarded to the inlinetool 50 b through the switch 70 b in the second inline-bypass switchappliance 10 b, as discussed.

If there is a power loss, or a powered down command, then the secondinline-bypass switch appliance 10 b may be placed back in the powereddown state.

As shown in the state diagram in FIG. 8C for the inline-bypass switchsystem 100, the inline-bypass switch system 100 may be (1) in theprimary forwarding state where one of the first and second inline-bypassswitch appliances 10 a, 10 b performs packet forwarding to itsassociated inline tool 50 a/50 b, (2) in the secondary forwarding statewhere the other one of the first and second inline-bypass switchappliances 10 a, 10 b performs packet forwarding to this associatedinline tool 50 a/50 b, or (3) in the bypass state where the first andsecond inline-bypass switch appliances 10 a, 10 b cooperate with eachother to pass packet from the node 22 to the node 26 without having thepacket processed by the inline tools 50 a, 50 b. For the purpose of thediscussion below, it will be assumed that the first inline-bypass switchappliance 10 a performs packet forwarding to its associated inline tool50 a in the primary forwarding state, and that the second inline-bypassswitch appliance 10 b performs packet forwarding to its associatedinline tool 50 b in the secondary forwarding state. However, thescenario may be reversed.

The inline-bypass switch system 100 can be placed in the primaryforwarding state whenever the first inline-bypass switch appliance 10 ahas a forwarding path established for passing packets to the inline tool50 a.

The inline-bypass switch system 100 can be placed in the secondaryforwarding state whenever the first inline-bypass switch appliance 10 ahas a power loss while the second inline-bypass switch appliance 10 b isin the bypass state (i.e., so that the second inline-bypass switchappliance 10 b is readily switchable to the forwarding state).

However, if the first inline-bypass switch appliance 10 a has a powerloss while the second inline-bypass switch appliance 10 b is in thepowered down state or path establishing state (i.e., so that the secondinline-bypass switch appliance 10 b is not ready to be placed in theforwarding state—see state diagram for the second inline-bypass switchappliance 10 b), then the system 100 is placed in the bypass state.

Similarly, if the second inline-bypass switch appliance 10 b has a powerloss while the first inline-bypass switch appliance 10 a is in thepowered down state or in the path establishing state (i.e., so that thefirst inline-bypass switch appliance 10 a is not ready to be placed inthe forwarding state—see state diagram for the first inline-bypassswitch appliance 10 a), then the system 100 is placed in the bypassstate.

FIGS. 9A-9B illustrate state diagrams for the bypass components 60 a, 60b in the first and second inline-bypass switch appliances 10 a, 10 b,respectively. As shown in FIG. 9A, the bypass component 60 a in thefirst inline-bypass switch appliance 10 a may be in a relays-closedstate or a relays-open state. The bypass component 60 a is in therelays-closed state by closing its relays when power at the firstinline-bypass switch appliance 10 a is turned off or is lost, or may beforced to be closed by the controller 80 a in response to a command,such as a software command, to force the relays to close. The bypasscomponent 60 a may be transitioned from the relays-closed state to therelays-open state by opening the relays therein when the traffic path(for forwarding packets to the inline tool 50 a) has been established atthe first inline-bypass switch appliance 10 a.

As shown in FIG. 9B, the bypass component 60 b in the secondinline-bypass switch appliance 10 b may also be in a relays-closed stateor a relays-open state. The bypass component 60 b is in therelays-closed state by closing its relays when power at the secondinline-bypass switch appliance 10 b is turned off, or when the signalinglink 110 is between the first and second inline-bypass switch appliances10 a, 10 b is transmitting an “up” signal. In one implementation, whenthe bypass component 60 a is in the relays-open state (corresponding tothe situation when the first inline-bypass switch appliance 10 a is up),the controller 80 a at the first inline-bypass switch appliance 10 asends a state signal (e.g., an “up” signal) to the second inline-bypassswitch appliance 10 b through the communication interface 102 a, toindicate that the bypass component 60 a is in the relays-open state. Insuch situation, the bypass component 60 b may be placed in therelays-closed state.

The bypass component 60 b is transitioned from the relays-closed stateto the relays-open state by opening the relays therein when thesignaling link 110 is transmitting a state signal of “down”, and if thetraffic path (for forwarding packets to the inline tool 50 b) has beenestablished at the second inline-bypass switch appliance 10 b. In oneimplementation, when the bypass component 60 a is in the relays-closedstate (corresponding to the situation when the first inline-bypassswitch appliance 10 a is down), the controller 80 a at the firstinline-bypass switch appliance 10 a sends a state signal (e.g., a “down”signal) to the second inline-bypass switch appliance 10 b through thecommunication interface 102 a, to indicate that the bypass component 60a is in the relays-closed state. In such situation, and if the packetforwarding path through the switch 70 b has already been established,then the bypass component 60 b may be placed in the relays-open state.

FIG. 10 illustrates another inline-bypass switch system 100 inaccordance with other embodiments. The inline-bypass switch system 100includes a first inline-bypass switch appliance 10 a, and a secondinline-bypass switch appliance 10 b. The inline-bypass switch system 100is configured to communicate packets between network nodes 22, 23 andnetwork nodes 26, 27.

In some cases, the node A1 22 and the node A2 23 may belong to a sameentity, in which cases, the node A1 22 and the node A2 23 may beredundant nodes for load sharing. In other cases, the node A1 22 and thenode A2 23 may belong to different respective users or entities, and maybe unrelated to each other. Similarly, in some cases, the node B1 26 andthe node B2 27 may belong to a same entity, in which cases, the node B126 and the node B2 27 may be redundant nodes for load sharing. In othercases, the node B1 26 and the node B2 27 may belong to differentrespective users or entities, and may be unrelated to each other.

The inline-bypass switch appliance 10 a has a first communicationinterface 20 a for communication with a first node A1 22, and a secondcommunication interface 24 a for communication with the secondinline-bypass switch appliance 10 b. The inline-bypass switch appliance10 a also includes a third communication interface 21 a forcommunication with a third node A2 23, and a fourth communicationinterface 25 a for communication with the second inline-bypass switchappliance 10 b.

The inline-bypass switch appliance 10 a also has a fifth communicationinterface 30 a and a sixth communication interface 32 a forcommunication with an inline tool 50 a, and a seventh communicationinterface 31 a and an eighth communication interface 33 a forcommunication with an inline tool 50 b.

As shown in the figure, the inline-bypass switch appliance 10 a alsoincludes a first bypass component 60 a, a second bypass component 60 b,a switch 70 a, and a controller 80 a. These components are accommodatedin a housing 90 a so that the inline-bypass switch appliance 10 a may betransported, sold, and deployed as a unit.

The first bypass component 60 a is configured to selectively transmitpackets received from the node A1 22 to the switch 70 a, or selectivelybypass the switch 70 a so that packets received at the firstcommunication interface 20 a will be passed directly through the bypasscomponent 60 a to the second communication interface 24 a.

The second bypass component 60 b is also configured to selectivelytransmit packets received from the node A2 23 to the switch 70 a, orselectively bypass the switch 70 a so that packets received at the thirdcommunication interface 21 a will be passed directly through the bypasscomponent 60 a to the fourth communication interface 25 a.

The switch 70 a is configured to pass packets to the inline tool 50 avia the fifth communication interface 30 a. After the inline tool 50 aprocesses the packets, the inline tool 50 a then returns the packets tothe first inline-bypass switch appliance 10 a through the sixthcommunication interface 32 a.

The switch 70 a is also configured to pass packets to the inline tool 50b via the seventh communication interface 31 a. After the inline tool 50b processes the packets, the inline tool 50 b then returns the packetsto the first inline-bypass switch appliance 10 a through the eighthcommunication interface 33 a.

In the illustrated example, two pairs of communication interfaces (i.e.,communication interfaces 30 a, 32 a, and communication interfaces 31 a,33 a) are provided for the two inline tools 50 a, 50 b, respectively. Inother examples, the inline-bypass switch appliance 10 a may include morethan two pairs of communication interfaces for communication with morethan two inline tools. The switch 70 a is configured to forward thepackets to one or more inline tools based on one or more parameters,such as IP source address, IP destination address, etc.

The controller 80 a is configured to control the operation of the firstbypass component 60 a, the second bypass component 60 b, and the switch70 a.

The second inline-bypass switch appliance 10 b has a first communicationinterface 20 b for communication with the first inline-bypass switchappliance 10 a through the second communication interface 24 a at thefirst inline-bypass switch appliance 10 a, and a second communicationinterface 24 b for communication with a second node B1 26. The secondinline-bypass switch appliance 10 b also includes a third communicationinterface 21 b for communication with the first inline-bypass switchappliance 10 a through the fourth communication interface 25 a at thefirst inline-bypass switch appliance 10 a, and a fourth communicationinterface 25 b for communication with a fourth node B2 27.

The second inline-bypass switch appliance 10 b also has a fifthcommunication interface 30 b and a sixth communication interface 32 bfor communication with an inline tool 50 b, and a seventh communicationinterface 31 b and an eighth communication interface 33 b forcommunication with an inline tool 50 a.

As shown in the figure, the second inline-bypass switch appliance 10 balso includes a first bypass component 60 c, a second bypass component60 d, a switch 70 b, and a controller 80 b. These components areaccommodated in a housing 90 b so that the second inline-bypass switchappliance 10 b may be transported, sold, and deployed as a unit.

The bypass component 60 c is configured to selectively transmit packetsreceived at the first communication interface 20 b of the secondinline-bypass switch appliance 10 b to the switch 70 b, or selectivelybypass the switch 70 b so that packets received at the firstcommunication interface 20 b will be passed directly through the bypasscomponent 60 c to the second communication interface 24 b (for receptionby the node B2 26).

The bypass component 60 d is configured to selectively transmit packetsreceived at the third communication interface 21 b of the secondinline-bypass switch appliance 10 b to the switch 70 b, or selectivelybypass the switch 70 b so that packets received at the thirdcommunication interface 21 b will be passed directly through the bypasscomponent 60 d to the fourth communication interface 25 b (for receptionby the node B2 27).

The switch 70 b is configured to pass packets to the inline tool 50 bvia the fifth communication interface 30 b. After the inline tool 50 bprocesses the packets, the inline tool 50 b then returns the packets tothe second inline-bypass switch appliance 10 b through the sixthcommunication interface 32 b.

The switch 70 b is also configured to pass packets to the inline tool 50a via the seventh communication interface 31 b. After the inline tool 50a processes the packets, the inline tool 50 a then returns the packetsto the second inline-bypass switch appliance 10 b through the eighthcommunication interface 33 b.

In the illustrated example, two pairs of communication interfaces (i.e.,communication interfaces 30 b, 32 b, and communication interfaces 31 b,33 b) are provided for the two inline tools 50 b, 50 a, respectively. Inother examples, second the inline-bypass switch appliance 10 b mayinclude more than two pairs of communication interfaces forcommunication with more than two inline tools. The switch 70 b isconfigured to forward the packets to one or more inline tools based onone or more parameters, such as IP source address, IP destinationaddress, etc.

The controller 80 b is configured to control the operation of the firstbypass component 60 c, the second bypass component 60 d, and the switch70 b in the second inline-bypass switch appliance 10 b.

As shown in FIG. 10, the appliance 10 a has a communication interface102 a, and that the appliance 10 b has a communication interface 102 b,for communication with each other through a signaling link 110. Thecontroller 80 a and/or the controller 80 b is configured to control thefirst inline-bypass switch appliance 10 a and the second inline-bypassswitch appliance 10 b, so that the inline-bypass switch system 100 canbe selectively placed in (1) a multi-operational state, (2) aprimary-operational state, (3) a secondary-operational state, or (4) abypass state.

FIG. 11 shows the inline-bypass switch system 100 in themulti-operational state. In the multi-operational state, the firstinline-bypass switch appliance 10 a is configured to receive packetsfrom the node 22 through the first communication interface 20 a. Therelays in the first bypass component 60 a are opened to pass the packetsto the switch 70 a. The switch 70 a then forwards the packets to theinline tools 50 a, 50 b through the fifth communication interface 30 aand the seventh communication interface 31 a, respectively. After thepackets are processed by the inline tools 50 a, 50 b, they are returnedback to the first inline-bypass switch appliance 10 a at the sixthcommunication interface 32 a, and the eighth communication interface 33a, respectively. The packets are transmitted through the switch 70 a andthe first bypass component 60 a, and are output at the secondcommunication interface 24 a of the first inline-bypass switch appliance10 a for reception by the first communication interface 20 b at thesecond inline-bypass switch appliance 10 b. At the second inline-bypassswitch appliance 10 b, the relays in the first bypass component 60 c areclosed, thereby passing the packets through the first bypass component60 c without having the packets processed by the switch 70 b. Thepackets are then transmitted out of the second communication interface24 b for reception by the node 26.

Also in the multi-operational state, the node 23 transmits packets forreception at the third communication interface 21 a at the firstinline-bypass switch appliance 10 a. The relays in the second bypasscomponent 60 b at the first inline-bypass switch appliance 10 a areclosed, thereby passing the packets to the fourth communicationinterface 25 a without having the packets processed by the switch 70 a.The packets are then output from the fourth communication interface 25 afor reception by the third communication interface 21 b at the secondinline-bypass switch appliance 10 b. The relays in the second bypasscomponent 60 d at the second inline-bypass switch appliance 10 b areopened, thereby passing the packets to the switch 70 b. The switch 70 bthen forwards the packets to the inline tool 50 b, and the inline tool50 a through the fifth communication interface 30 b and the seventhcommunication interface 31 b, respectively. After the inline tools 50 b,50 a process the packets, the packets are returned back to the secondinline-bypass switch appliance 10 b at the sixth communication interface32 b and the eighth communication interface 33 b, respectively. Thepackets are transmitted through the switch 70 b and the second bypasscomponent 60 d, and are output at the fourth communication interface 25b for reception by the node 27.

Accordingly, as shown in the above example, in the multi-operationalstate, packets from the transmitting node 22 are processed by the switch70 a in the first inline-bypass switch appliance 10 a, and are processedby the inline tools 50 a, 50 b. Also, packets from the transmitting node23 are processed by the switch 70 b in the second inline-bypass switchappliance 10 b, and are processed by the inline tools 50 a, 50 b. Thisconfiguration is advantageous because the first and second inline-bypassswitch appliances 10 a, 10 b can be configured to share loads betweenthe nodes 22, 23. Also, the inline tools 50 a, 50 b can be configured toshare loads from the node 22, and also to share loads from the node 23.

Although the above example is described with reference to the nodes 22,23 being network transmitting nodes, in other cases, the nodes 22, 23may be network receiving nodes. In such cases, the nodes 26, 27 arenetwork transmitting nodes, and the above described packet flow may bereversed in direction.

FIG. 12 shows the inline-bypass switch system 100 in theprimary-operational state. In the primary operational state, the secondinline-bypass switch appliance 10 b fails to forward packets from thenodes 22, 23 to the inline tools 50 a, 50 b, and the first inline-bypassswitch appliance 10 a is configured to forward packets from the nodes22, 23 to the inline tools 50 a, 50 b. In the primary operational state,the first communication interface 20 a receives packets from the node22. The relays in the first bypass component 60 a are opened, therebypassing the packets to the switch 70 a. The switch 70 a forwards thepackets to the inline tools 50 a, 50 b through the fifth communicationinterface 30 a and the seventh communication interface 31 a,respectively. After the inline tools 50 a, 50 b process the packets, theinline tools 50 a, 50 b return the packets to the first inline-bypassswitch appliance 10 a at the sixth communication interface 32 a and theeighth communication interface 33 a, respectively. The packets aretransmitted through the switch 70 a, and the first bypass component 60a. The packets are then output through the second communicationinterface 24 a for reception by the first communication interface 20 bat the second inline-bypass switch appliance 10 b. At the secondinline-bypass switch appliance 10 b, the relays in the first bypasscomponent 60 c are closed, thereby passing the packets through the firstbypass component 60 c without having the packets processed by the switch70 b. The packets are output at the second communication interface 24 bfor reception by the node 26.

Also in the primary-operational state, the third communication interface21 a receives packets from the node 23. The relays in the second bypasscomponent 60 b are opened, thereby passing the packets to the switch 70a. The switch 70 a forwards the packets to the inline tools 50 a, 50 bthrough the fifth communication interface 30 a and the seventhcommunication interface 31 a, respectively. After the inline tools 50 a,50 b process the packets, the inline tools 50 a, 50 b return the packetsto the first inline-bypass switch appliance 10 a at the sixthcommunication interface 32 a and the eighth communication interface 33a, respectively. The packets are transmitted through the switch 70 a,and the second bypass component 60 b. The packets are then outputthrough the fourth communication interface 25 a for reception by thethird communication interface 21 b at the second inline-bypass switchappliance 10 b. At the second inline-bypass switch appliance 10 b, therelays in the second bypass component 60 d are closed, thereby passingthe packets through the first bypass component 60 d without having thepackets processed by the switch 70 b. The packets are output at thefourth communication interface 25 b for reception by the node 27.

Accordingly, as shown in the example, even if the second inline-bypassswitch appliance 10 b is down, the first inline-bypass switch appliance10 a can still forward packets from the nodes 22, 23 to the inline tools50 a, 50 b, and then pass the packets to the receiving nodes 26, 27.

Although the above example is described with reference to the nodes 22,23 being network transmitting nodes, in other cases, the nodes 22, 23may be network receiving nodes. In such cases, the nodes 26, 27 arenetwork transmitting nodes, and the above described packet flow may bereversed in direction.

FIG. 13 shows the inline-bypass switch system 100 in thesecondary-operational state. In the secondary operational state, thefirst inline-bypass switch appliance 10 a fails to forward packets fromthe nodes 22, 23 to the inline tools 50 a, 50 b, and the secondinline-bypass switch appliance 10 b is configured to forward packetsfrom the nodes 22, 23 to the inline tools 50 a, 50 b. In the secondaryoperational state, the first communication interface 20 a receivespackets from the node 22. The relays in the first bypass component 60 aare closed, thereby passing the packets through the first bypasscomponent 60 a without having the packets processed by the switch 70 a.The packets are then transmitted out of the second communicationinterface 24 a for reception by the first communication interface 20 bat the second inline-bypass switch appliance 10 b. At the secondinline-bypass switch appliance 10 b, the relays in the first bypasscomponent 60 c are opened, thereby passing the packets to the switch 70b. The switch 70 b then forwards the packets to the inline tools 50 b,50 a through the fifth communication interface 30 b and the seventhcommunication interface 31 b. After the inline tools 50 b, 50 a processthe packets, the packets are returned to the second inline-bypass switchappliance 10 b at the sixth communication interface 32 b and the eighthcommunication interface 33 b, respectively. The packets are transmittedthrough the switch 70 b and the first bypass component 60 c. The packetsare then output at the second communication interface 24 b at the secondinline-bypass switch appliance 10 b for reception by the node 26.

Also, in the secondary-operational state, the third communicationinterface 21 a receives packets from the node 23. The relays in thesecond bypass component 60 b are closed, thereby passing the packetsthrough the second bypass component 60 b without having the packetsprocessed by the switch 70 a. The packets are then transmitted out ofthe fourth communication interface 25 a for reception by the thirdcommunication interface 21 b at the second inline-bypass switchappliance 10 b. At the second inline-bypass switch appliance 10 b, therelays in the second bypass component 60 d are opened, thereby passingthe packets to the switch 70 b. The switch 70 b then forwards thepackets to the inline tools 50 b, 50 a through the fifth communicationinterface 30 b and the seventh communication interface 31 b. After theinline tools 50 b, 50 a process the packets, the packets are returned tothe second inline-bypass switch appliance 10 b at the sixthcommunication interface 32 b and the eighth communication interface 33b, respectively. The packets are transmitted through the switch 70 b andthe second bypass component 60 d. The packets are then output at thefourth communication interface 25 b at the second inline-bypass switchappliance 10 b for reception by the node 27.

Accordingly, as shown in the example, even if the first inline-bypassswitch appliance 10 a is down, the second inline-bypass switch appliance10 b can still forward packets from the nodes 22, 23 to the inline tools50 a, 50 b, and then pass the packets to the receiving nodes 26, 27.

Although the above example is described with reference to the nodes 22,23 being network transmitting nodes, in other cases, the nodes 22, 23may be network receiving nodes. In such cases, the nodes 26, 27 arenetwork transmitting nodes, and the above described packet flow may bereversed in direction.

FIG. 14 shows the inline-bypass switch system 100 in the bypass state.In the bypass state, the first and second inline-bypass switchappliances 10 a, 10 b both fail to forward packets from the nodes 22, 23to the inline tools 50 a, 50 b, and packets from the nodes 22, 23 arepassed to the nodes 26, 27 without being processed by the inline tools50 a, 50 b. In the bypass state, the first communication interface 20 areceives packets from the node 22. The relays in the first bypasscomponent 60 a are closed, thereby passing the packets through the firstbypass component 60 a without having the packets processed by the switch70 a. The packets are then transmitted out of the second communicationinterface 24 a for reception by the first communication interface 20 bat the second inline-bypass switch appliance 10 b. At the secondinline-bypass switch appliance 10 b, the relays in the first bypasscomponent 60 c are also closed, thereby passing the packets through thefirst bypass component 60 c without having the packets processed by theswitch 70 b. The packets are the transmitted out of the secondcommunication interface 24 b for reception by the node 26.

Also, in the bypass state, the third communication interface 21 areceives packets from the node 23. The relays in the second bypasscomponent 60 b are closed, thereby passing the packets through thesecond bypass component 60 b without having the packets processed by theswitch 70 a. The packets are then transmitted out of the fourthcommunication interface 25 a for reception by the third communicationinterface 21 b at the second inline-bypass switch appliance 10 b. At thesecond inline-bypass switch appliance 10 b, the relays in the secondbypass component 60 d are also closed, thereby passing the packetsthrough the second bypass component 60 d without having the packetsprocessed by the switch 70 b. The packets are the transmitted out of thefourth communication interface 25 b for reception by the node 27.

Accordingly, as shown in the above example, even when both the first andsecond inline-bypass switch appliances 10 a, 10 b are down, they canstill pass packets between transmitting nodes 22, 23, and receivingnodes 26, 27.

Although the above example is described with reference to the nodes 22,23 being network transmitting nodes, in other cases, the nodes 22, 23may be network receiving nodes. In such cases, the nodes 26, 27 arenetwork transmitting nodes, and the above described packet flow may bereversed in direction.

In some embodiments, the controller 80 a in the first inline-bypassswitch appliance 10 a is configured to keep track of the states of thefirst and second bypass components 60 a, 60 b, and provide respectivestate signals that represent the respective states of the bypasscomponents 60 a, 60 b. The controller 80 b in the second inline-bypassswitch appliance 10 b is configured to control the first and secondbypass components 60 c, 60 d based on the state signals received throughthe signaling link 110.

Also, in some embodiments, a state signal with a single value may beused to represent both the state of the first bypass component 60 a, andthe state of the second bypass component 60 b. For example, in oneimplementation, a state signal of “1” may represent the condition whenboth bypass components 60 a, 60 b are open, a state signal of “2” mayrepresent the condition when the first bypass component 60 a is open andthe second bypass component 60 b is closed, a state signal of “3” mayrepresent the condition when the first bypass component 60 a is closedand the second bypass component 60 b is open, and a state signal of “4”may represent the condition when the first bypass component 60 a and thesecond bypass component 60 b are closed. Accordingly, the secondcontroller 80 b may operate the bypass components 60 c, 60 d in thesecond inline-bypass switch appliance 10 b based on the single valuestate signal.

In some embodiments, the first controller 80 a may be configured toprovide a first state signal having a first value when the first bypasscomponent 60 a in the first inline-bypass switch appliance 10 a is in arelays-open state. In such cases, the second controller 80 b isconfigured to place the third bypass component 60 c in the secondinline-bypass switch appliance 10 b in a relays-closed state when thefirst state signal has the first value.

In other cases, the first state signal may have a second value that isdifferent from the first value when the first bypass component 60 a inthe first inline-bypass switch appliance 10 a is in a relays-closedstate. In such cases, the second controller 80 b is configured to placethe third bypass component 60 c in the second inline-bypass switchappliance 10 b in a relays-open state when the first state signal hasthe second value and when a packet forwarding path through the secondswitch 70 b has been established.

Similarly, in some embodiments, the first controller 80 a may beconfigured to provide a second state signal having a first value whenthe second bypass component 60 b in the first inline-bypass switchappliance 10 a is in a relays-open state. In such cases, the secondcontroller 80 b is configured to place the fourth bypass component 60 din the second inline-bypass switch appliance 10 b in a relays-closedstate when the second state signal has the first value.

In other cases, the second state signal may have a second value that isdifferent from the first value when the second bypass component 60 b inthe first inline-bypass switch appliance 10 a is in a relays-closedstate. In such cases, the second controller 80 b is configured to placethe fourth bypass component 60 d in the second inline-bypass switchappliance 10 b in a relays-open state when the second state signal hasthe second value and when a packet forwarding path through the secondswitch 70 b has been established.

Also, in some embodiments, the first controller 80 a is configured toclose the first bypass component 60 a when a packet forwarding paththrough the first switch 70 a has not been established, the firstcontroller 80 a is configured to open the first bypass component 60 awhen the packet forwarding path through the first switch 70 a has beenestablished, the second controller 80 b is configured to open the thirdbypass component 60 c when a packet forwarding path through the secondswitch 70 b has been established and when the first bypass component 60a is closed, and the second controller 80 b is configured to open thethird bypass component 60 c when the packet forwarding path through thesecond switch 70 b has not been established.

Similarly, in some embodiments, the first controller 80 a is configuredto close the second bypass component 60 b when a packet forwarding paththrough the first switch 70 a has not been established, the firstcontroller 80 a is configured to open the second bypass component 60 bwhen the packet forwarding path through the first switch 70 a has beenestablished, the second controller 80 b is configured to open the fourthbypass component 60 d when a packet forwarding path through the secondswitch 70 b has been established and when the second bypass component 60b is closed, and the second controller 80 b is configured to open thefourth bypass component 60 d when the packet forwarding path through thesecond switch 70 b has not been established.

Also, in some embodiments, the bypass components 60 a-60 d are naturallyin a relays-closed state when there is no power in the first and secondinline-bypass switch appliances 10 a, 10 b.

It should be noted that the above examples have been described withreference to the inline-bypass switch appliance(s) being incommunication with inline tool(s). In other embodiments, instead ofinline tool(s), the switch appliance(s) described herein may becommunicatively coupled to one or more non-inline tools.

Also, in the above examples, the state signal being provided by thecontroller 70 and transmitted via the signaling link 110 has beendescribed as being in a “down” state or “up” state. In otherembodiments, the state signal may have other values. For example, inother embodiments, the state signal may have a first state value (e.g.,“1”) when the first inline-bypass switch appliance 10 a is down (e.g.,in which case, the relays in the first bypass component 60 a areclosed), and a second state value (e.g., “0”) that is different from thefirst state value when the first inline-bypass switch appliance 10 a isup (e.g., in which case, the relays in the first bypass component 60 aare open).

It should be noted that the arrangements of the inline tools are notlimited to the examples described above, and that there are manypossible arrangements of sets of inline tools attached to theinline-bypass switch appliances. For example, while sets of one or moreinline tools may be dedicated to the first inline-bypass switchappliance 10 a and to the second inline-bypass switch appliance 10 b,respectively (like that described with reference to FIG. 4), in otherembodiments, one or more inline tools may be shared between the firstand second inline-bypass switch appliances 10 a, 10 b. As anotherexample, while sets of one or more inline tools may be shared betweenthe first and second inline-bypass switch appliances 10 a, 10 b (likethat described with reference to FIG. 10), in other embodiments, one ormore inline tools may be shared between the first and secondinline-bypass switch appliances 10 a, 10 b. The redundant arrangement ofinline-bypass switch appliances described herein applies to anyconfiguration of inline tools because the solution deals with decidingwhether the traffic on a particular appliance is guided through theinline tools attached to the appliance or bypassed.

Also, in some embodiments, the set of one or more inline toolsassociated with the first inline-bypass switch appliance 10 a may havethe same configuration (e.g., perform one or more functions that are thesame) as the set of one or more inline tools associated with the secondinline-bypass switch appliance 10 b. In other embodiments, the set ofone or more inline tools associated with the first inline-bypass switchappliance 10 a may have a different configuration (e.g., perform one ormore functions that are the different) as the set of one or more inlinetools associated with the second inline-bypass switch appliance 10 b.

It should be noted that when a “packet” is described in thisapplication, it should be understood that it may refer to the originalpacket that is transmitted from a node, or a copy of it. Also, a“packet” may refer to any part of a packet. For example, a “packet” maybe a header of a packet, a payload of a packet, or both.

It should be noted that the terms “first”, “second”, etc., are used torefer to different things, and do not necessarily refer to the order ofthings.

Although particular embodiments have been shown and described, it willbe understood that they are not intended to limit the claimedinventions, and it will be obvious to those skilled in the art thatvarious changes and modifications may be made without departing from thespirit and scope of the claimed inventions. The specification anddrawings are, accordingly, to be regarded in an illustrative rather thanrestrictive sense. The claimed inventions are intended to coveralternatives, modifications, and equivalents.

What is claimed:
 1. An inline-bypass switch system, comprising: a firstinline-bypass switch appliance having a first bypass component, a firstswitch coupled to the first bypass component, and a first controller;and a second inline-bypass switch appliance having a second bypasscomponent, a second switch coupled to the second bypass component, and asecond controller; wherein the first controller in the firstinline-bypass switch appliance is configured to provide a state signalthat is associated with a state of the first inline-bypass switchappliance; and wherein the second controller in the second inline-bypassswitch appliance is configured to control the second bypass componentbased at least in part on the state signal.
 2. The inline-bypass switchsystem of claim 1, wherein the first switch is configurable to performpacket forwarding to a first set of one or more inline tools, and thesecond switch is configurable to perform packet forwarding to a secondset of one or more inline tools.
 3. The inline-bypass switch system ofclaim 1, wherein the first bypass component and the second bypasscomponent are operable to place the inline-bypass switch system in oneof at least three states, the three states comprising: a primaryforwarding state in which the first inline-bypass switch appliance isconfigured to perform packet forwarding to the first set of the one ormore inline tools; a secondary forwarding state in which the secondinline-bypass switch appliance is configured to perform packetforwarding to the second set of the one or more inline tools; and aphysical bypass state in which the first inline-bypass switch appliancedoes not perform packet forwarding to the first set of the one or moreinline tools, and the second inline-bypass switch appliance does notperform packet forwarding to the second set of the one or more inlinetools.
 4. The inline-bypass switch system of claim 1, wherein the firstcontroller is configured to provide the state signal having a firstvalue when the first bypass component in the first inline-bypass switchappliance is in a relays-open state; and wherein the second controlleris configured to place the second bypass component in the secondinline-bypass switch appliance in a relays-closed state when the statesignal has the first value.
 5. The inline-bypass switch system of claim4, wherein the first controller is configured to provide the statesignal having a second value that is different from the first value whenthe first bypass component in the first inline-bypass switch applianceis in a relays-closed state; and wherein the second controller isconfigured to place the second bypass component in the secondinline-bypass switch appliance in a relays-open state when the statesignal has the second value and when a packet forwarding path throughthe second switch has been established.
 6. The inline-bypass switchsystem of claim 1, wherein the first inline-bypass switch appliancecomprises a first communication interface for receiving a packet from anetwork node, a second communication interface for outputting the packetto the second inline-bypass switch appliance, and a third communicationinterface for outputting the state signal for reception by the secondinline-bypass switch appliance.
 7. The inline-bypass switch system ofclaim 1, wherein the second inline-bypass switch appliance comprises afirst communication interface for receiving a packet from the firstinline-bypass switch appliance, a second communication interface foroutputting the packet to a network node, and a third communicationinterface for receiving the state signal from the first inline-bypassswitch appliance.
 8. The inline-bypass switch system of claim 1, whereinthe first bypass component has multiple relays; wherein when the relaysare closed, the first bypass component is in a relays-closed state, andwhen the relays are opened, the first bypass component is in arelays-open state.
 9. The inline-bypass switch system of claim 8,wherein the first controller is configured to place the first bypasscomponent in the relays-open state when a packet forwarding path throughthe first switch has been established.
 10. The inline-bypass switchsystem of claim 9, wherein the state signal has a value that representsthe first bypass component being in the relays-open state.
 11. Theinline-bypass switch system of claim 8, wherein the first controller isconfigured to place the first bypass component in the relays-closedstate when a packet forwarding path through the first switch has notbeen established.
 12. The inline-bypass switch system of claim 11,wherein the state signal has a value that represents the first bypasscomponent being in the relays-closed state.
 13. A first inline-bypassswitch appliance, comprising: a first bypass component; a first switchcoupled to the first bypass component, the first switch configured tocommunicate with one or more inline tools; a first controller configuredto provide a state signal that is associated with a state of the firstbypass component; a first communication interface configured to receivea packet from a first network node; a second communication interfaceconfigured to output the packet to a second inline-bypass switchappliance; and a third communication interface configured to output thestate signal for reception by the second inline-bypass switch appliance.14. The first inline-bypass switch appliance of claim 13, wherein thefirst bypass component is operable to be in a relays-closed state, andis operable to be in a relays-open state; wherein when the first bypasscomponent is in the relays-closed state, the first bypass component isconfigured to pass the packet from the first communication interface tothe second communication interface without passing the packet to thefirst switch; and wherein when the first bypass component is in therelays-open state, the first bypass component is configured to pass thepacket from the first communication interface to the first switch. 15.The first inline-bypass switch appliance of claim 13, wherein the firstbypass component comprises one or more relays.
 16. The firstinline-bypass switch appliance of claim 15, wherein the first controlleris configured to close the one or more relays in the first bypasscomponent when a packet forwarding path through the first switch has notbeen established or when the first inline-bypass switch appliance ispowered down; and wherein the first controller is configured to open theone or more relays in the first bypass component when the packetforwarding path through the first switch has been established.
 17. Thefirst inline-bypass switch appliance of claim 13, wherein the statesignal has a first value when the state of the first bypass component isin the first state, and wherein the state signal has a second value thatis different from the first value when the state of the first bypasscomponent is in the second state.
 18. The first inline-bypass switchappliance of claim 13, wherein the first bypass component has one ormore relays that are closed whenever there is a power loss for the firstinline-bypass switch appliance.
 19. An inline-bypass switch systemcomprising the first inline-bypass switch appliance of claim 13, and thesecond inline-bypass switch appliance.
 20. The inline-bypass switchsystem of claim 19, wherein the second inline-bypass switch appliancecomprises: a second bypass component; a second switch coupled to thesecond bypass component; a second controller; a first communicationinterface configured to receive the packet from the second communicationinterface of the first inline-bypass switch appliance; a secondcommunication interface configured to output the packet to a secondnetwork node; and a third communication interface configured to receivethe state signal; wherein the second controller is configured toselectively place the second bypass component in a first state or asecond state.
 21. The inline-bypass switch system of claim 20, whereinthe first state of the second bypass component comprises a relays-closedstate, and the second state of the second bypass component comprises arelays-open state; wherein when the second bypass component is in therelays-closed state, the second bypass component is configured to passthe packet from the first communication interface of the secondinline-bypass switch appliance to the second communication interface ofthe second inline-bypass switch appliance without passing the packet tothe second switch; and wherein when the second bypass component is inthe relays-open state, the second bypass component is configured to passthe packet from the first communication interface of the secondinline-bypass switch appliance to the second switch.
 22. Theinline-bypass switch system of claim 20, wherein the second bypasscomponent comprises one or more relays.
 23. The inline-bypass switchsystem of claim 22, wherein the second controller is configured to closethe one or more relays in the second bypass component when one or morerelays in the first bypass component are open; wherein the secondcontroller is configured to open the one or more relays in the secondbypass component when the one or more relays in the first bypasscomponent are closed, and when a packet forwarding path through thesecond switch has been established; and wherein the second controller isconfigured to close the one or more relays in the second bypasscomponent when the one or more relays in the first bypass component areclosed, and when the packet forwarding path through the second switchhas not been established.
 24. The inline-bypass switch system of claim20, wherein the second controller of the second inline-bypass switchappliance is configured to control the second bypass component based atleast in part on the state signal received from the first inline-bypassswitch appliance.
 25. An inline-bypass switch appliance, comprising: abypass component; a switch configured to communicate with one or moreinline tools; a controller; a first communication interface configuredto receive a packet from another inline-bypass switch appliance; asecond communication interface configured to output the packet to anetwork node; and a third communication interface configured to receivea state signal from the other inline-bypass switch appliance, the statesignal being associated with a state of another bypass component in theother inline-bypass switch appliance; wherein the controller isconfigured to control the bypass component based at least in part on thestate signal.
 26. The inline-bypass switch appliance of claim 25,wherein the bypass component is operable to be in a relays-closed state,and is operable to be in a relays-open state; wherein when the bypasscomponent is in the relays-closed state, the bypass component isconfigured to pass the packet from the first communication interface tothe second communication interface without passing the packet to theswitch; and wherein when the bypass component is in the relays-openstate, the bypass component is configured to pass the packet from thefirst communication interface to the switch.
 27. The inline-bypassswitch appliance of claim 25, wherein the bypass component comprises oneor more relays.
 28. The inline-bypass switch appliance of claim 27,wherein the controller is configured to close the one or more relays inthe bypass component when one or more relays in the other bypasscomponent are open; wherein the controller is configured to open the oneor more relays in the bypass component when the one or more relays inthe other bypass component are closed, and when a packet forwarding paththrough the switch has been established; and wherein the controller isconfigured to close the one or more relays in the bypass component whenthe one or more relays in the other bypass component are closed, andwhen the packet forwarding path through the switch has not beenestablished.